Rather than writing a plugin for the Arduino IDE what about using the option in the IDE for an external editor. Then you could write a program to convert the Arabic in the editor text file into an english version for the Arduino to verify and load.
This would mean that the student could have both the Arabic original and the English "translation" side by side. (I'm not sure whether you would consider that an advantage).
The "translation" program might just need to go through the Arabic file looking for key words and replacing them with the English equivalent. If you are aiming the product at beginners you might only need to allow for the common key words and not the more obscure C/C++ stuff.
It may also need to swap the order of all the words and symbols to left-to-right but that may be fairly simple to do.
...R